Measurement of the J/ψ Polarization with Respect to the Event Plane in Pb-Pb Collisions at the LHC.



Acharya, S ORCID: 0000-0002-9213-5329, Adamová, D ORCID: 0000-0002-0504-7428, Adler, A, Aglieri Rinella, G, Agnello, M, Agrawal, N ORCID: 0000-0003-0348-9836, Ahammed, Z ORCID: 0000-0001-5241-7412, Ahmad, S ORCID: 0000-0003-0497-5705, Ahn, SU ORCID: 0000-0001-8847-489X, Ahuja, I ORCID: 0000-0002-4417-1392
et al (show 1022 more authors) (2023) Measurement of the J/ψ Polarization with Respect to the Event Plane in Pb-Pb Collisions at the LHC. Physical review letters, 131 (4). 042303-. ISSN 0031-9007, 1079-7114

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Abstract

We study the polarization of inclusive J/ψ produced in Pb-Pb collisions at sqrt[s_{NN}]=5.02  TeV at the LHC in the dimuon channel, via the measurement of the angular distribution of its decay products. We perform the study in the rapidity region 2.5<y<4, for three transverse momentum intervals (2<p_{T}<4, 4<p_{T}<6, 6<p_{T}<10  GeV/c) and as a function of the centrality of the collision for 2<p_{T}<6  GeV/c. For the first time, the polarization is measured with respect to the event plane of the collision, by considering the angle between the positive-charge decay muon in the J/ψ rest frame and the axis perpendicular to the event-plane vector in the laboratory system. A small transverse polarization is measured, with a significance reaching 3.9σ at low p_{T} and for intermediate centrality values. The polarization could be connected with the behavior of the quark-gluon plasma, formed in Pb-Pb collisions, as a rotating fluid with large vorticity, as well as with the existence of a strong magnetic field in the early stage of its formation.

Item Type: Article
Uncontrolled Keywords: ALICE Collaboration
Divisions: Faculty of Science and Engineering > School of Physical Sciences
Depositing User: Symplectic Admin
Date Deposited: 03 Oct 2023 15:14
Last Modified: 07 Dec 2024 23:37
DOI: 10.1103/physrevlett.131.042303
Open Access URL: https://doi.org/10.1103/PhysRevLett.131.042303
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URI: https://livrepository.liverpool.ac.uk/id/eprint/3173371